Back to EveryPatent.com
United States Patent | 5,289,152 |
Oguriyama ,   et al. | February 22, 1994 |
A permanent magnet magnetic circuit is provided capable of producing a unidirectional magnetic field substantially free of unnecessary perpendicular magnetic field components. A pair of main magnetic poles of opposite polarities are situated at a pair of opposite edge surfaces of a permanent magnet block for producing lines of magnetic force. One major surface of the block between the edge surfaces is provided with a channel where a pair of auxiliary magnetic poles are situated at opposed inner surface portions of the channel for controlling a middle portion of the lines of magnetic force to be linear.
Inventors: | Oguriyama; Masami (Ichikawa, JP); Ishigaki; Yoshio (Ichikawa, JP); Okano; Haruo (Tokyo, JP); Hasegawa; Isahiro (Zushi, JP); Arami; Jun-ichi (Hachioji, JP); Harada; Hiromi (Hiratsuka, JP) |
Assignee: | TDK Corporation (Tokyo, JP); Kabushiki Kaisha Toshiba (Kawasaki, JP); Tokyo Electron Limited (Tokyo, JP) |
Appl. No.: | 047054 |
Filed: | April 12, 1993 |
Sep 19, 1990[JP] | 2-249040 |
Current U.S. Class: | 335/302 |
Intern'l Class: | H01F 007/02 |
Field of Search: | 335/210-212,296,297,302,304,306 315/5.35 250/396 ML 310/90.5 204/298.16-298.22 |
2925517 | Feb., 1960 | Glass | 335/210. |
4461688 | Jul., 1984 | Morrison. | |
4614930 | Sep., 1986 | Hickey et al. | 335/302. |
4672346 | Jun., 1987 | Miyamoto | 335/296. |
4810986 | Mar., 1989 | Leupold | 335/304. |
4842707 | Jul., 1989 | Kinoshita | 204/298. |
4964968 | Oct., 1990 | Arita | 204/298. |
Foreign Patent Documents | |||
969151 | May., 1958 | DE | 335/302. |
1287672 | Jan., 1969 | DE | 335/306. |
58-130277 | Aug., 1983 | JP. | |
63-250458 | Oct., 1988 | JP. | |
0163371 | Jun., 1990 | JP | 204/298. |